Coaxial cable television systems have been in widespread use for many years and extensive networks have been developed. The extensive and complex networks are often difficult for a cable operator to manage and monitor. A typical cable network generally contains a headend which is usually connected to several nodes which provide content to a cable modem termination system (CMTS) containing several receivers, each receiver connects to several modems of many subscribers, e.g., a single receiver may be connected to hundreds of modems. In many instances several nodes may serve a particular area of a town or city. The modems communicate to the CMTS via upstream communications on a dedicated band of frequency.
Cable networks are also increasingly carrying signals which require a high quality and reliability of service, such as voice communications or Voice over IP (VoIP) communications. Any disruption of voice or data traffic is a great inconvenience and often unacceptable to a subscriber. Various factors may affect the quality of service, including the quality of the upstream channels. One factor that affects the quality of upstream communications is the presence of micro-reflections of communication signals.
A micro-reflection is a copy of a communication signal, such as a signal reflected back onto itself, but delayed in time. There are two significant causes of micro-reflections in an upstream HFC plant, impedance mismatches and diplex filters. Significant micro-reflections can degrade upstream HFC plant performance. Accurately diagnosing micro-reflection issues typically requires technicians or engineers to be at multiple locations within the HFC plant and simultaneously inject test signals at the suspected device locations. The presence of micro-reflections is then detected at the headend location with specialized test equipment, such as a vector signal analyzer. This diagnostic process requires extensive manual effort, often requiring rolling trucks to remote locations within a plant or specialized test equipment. The diagnostic process is also time consuming and costly. Accordingly an automated process to determine whether micro-reflections are appreciably degrading the upstream HFC plant performance is needed which does not significantly impact the HFC network, is cost effective and does not require specialized equipment.